Rotatable article, such as a tool, provided with means for damping vibration

ABSTRACT

The article, such as a circular saw tool or a gear wheel, has a visco-elastic synthetic-resin damping layer between, on the one hand, a portion of the body of the article which is integral with, or securely attached to, a work region adapted to interact with another article, and, on the other hand, a counter-element which extends parallel thereto. The damping layer is arranged in the interior of the article in a region covered by an outer member integral with or securely connected to the body. The parts between which the damping layer lies are connected together by the damping layer in a manner which permits shear stresses to occur in the damping layer.

This is a divisional of application Ser. No. 003,786, filed Jan. 15,1979, now U.S. Pat. No. 4,285,260.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a disc-like rotatable article having vibrationdamping means and comprising a body with a work region (e.g. havingteeth or one or more cutting blades) adapted to interact with anotherarticle (e.g. a workpiece or another disc-like rotatable article).

2. Description of the Prior Art

The reduction of noise occurring during idling running and particularlyduring the working or chip removing process of rotating parts, inparticular tools such as saw blades, constitutes an urgent but difficultproblem. This applies particularly to tools for the treatment of woodand synthetic resin, but also for metal-working, for example light-metalsaws, tools for the machining of steel, and so on.

It has been found that a reduction of the noise may be obtained for acircular saw tool if the tool body forming the so-called stock blade isprovided on at least one side, preferably on both sides, with a dampinglayer formed by an adhesive and a cover arranged on it as acounter-element, namely by damping the saw-blade vibrations causing thenoise. The layer in the form of an adhesive not only has the purpose ofattaching and retaining the cover on the respective part of the tool,but at the same time it fulfils an important function in respect ofvibration damping. The externally excited or self excited vibrations ofthe rotating tool cause respective thrust motions between the cover andthe tool body proper (stock blade), whereby corresponding shear stressesare produced in the damping layer.

It is important for the use of tools of such construction that theelements located on the damping layers retain their position and are notreleased by the loads occurring. On the other hand, however, as high adamping as possible is to be attached. Therefore demands are involvedwhich contradict each other to a large extent.

There is therefore a need to overcome existing difficulties and defectsand to provide an article of the kind referred to above which hasadvantageous properties, and to construct it in such a manner that itcan comply with a variety of requirements. This applies in particular inrespect of favourable stiffness conditions, mechanical strength,effective protection of the damping system, and reliableholding-together of the parts associated therewith, while at the sametime attaining a highly satisfactory damping effect. With all this, theloads to be expected in practical use, particularly those on the outeror lateral portions of the article, should be absorbed reliably.

SUMMARY OF THE INVENTION

According to the invention, in a tool or other rotatable article havingat least one damping layer and an associated counter-element, thedamping layer is arranged in the interior of the article in a regionwhich is covered outwardly by an outer member which is securely attachedto the body of the article or tool or forms a part thereof, wherein theparts imprisoning between them the damping layer are connected togetherby means of the damping layer in a manner which permits shear stressesto occur therein.

The invention provides a tool, for example a circular saw tool, oranother article which rotates in operation, such as a transmissionelement, e.g. a gear wheel, which is characterised by a number ofimportant advantages. The damping layer is accommodated in a completelyprotected manner, so that it cannot be damaged or destroyed. The outermember is effectively part of the body of the article and may be sodimensioned that a high static stiffness of this outer member and thusof the entire body of the article results therefrom. Thereby thevibration tendency of the tool or other article is considerably reducedand also the load-bearing ability during operation is influenced in afavourable manner, because mechanical loads inclusive of friction forcesacting upon the lateral surfaces, as well as thermal loads, can beabsorbed in a reliable manner. Furthermore the dynamic stiffness of thearticle is increased, this being particularly advantageous for thedamping behaviour. Moreover, the outer member also contributes to thescreening effect, i.e. for shielding body sound.

Advantageously two or more damping layers with associatedcounter-elements are present, particularly in a symmetrical arrangementin relation to a central plane of the article. The respective dampinglayer is preferably arranged outside the neutral fibre layer, i.e. therespective location or plane in which, when a load occurs, the stress inthe material is zero, whereas it assumes positive values (compression)on the one side and negative values (tension) on the other side. In adisc-shaped article, corresponding loads result inter alia with axialvibrations, which are generally causative for noise generation. In asymmetrically constructed tool, e.g. a circular saw blade, the neutralfibre layer is located in the central plane.

As damping layer in particular an adhesive comes into considerationwhich has suitable properties, for example a loss factor η=0.5 to 2 inthe range of from 1 to 5 kHz. In comparison with the material of thebody of the article and the outer members or the counter elements,respectively, the material for the damping layer has a low elasticitymodulus. This, too, leads to effective shielding of the body sound. Inparticular, the elasticity modulus may amount to (0.5 to 5)·10⁹ dyn/cm².

In a preferred embodiment of the article the outer member is securelyconnected to the work region, for example, in a saw tool, to theperipheral region supporting the teeth, in such a manner that the memberitself forms a body which is directly involved in the absorption of theworking forces.

The body of the tool or article may comprise at least one chamber inwhich at least one damping layer and at least one counter-elementlocated thereon is disposed. In this case various possibilities exist inrespect of the construction in detail and the arrangement of theelements. Thus, inter alia, a damping layer may be provided on the basesurface of the chamber. Alternatively or additionally, a damping layermay be arranged on the inside of the outer member. In this case anadvantageous large spacing may be obtained from the plane of the tool orarticle which must be regarded as neutral fibre layer in relation tovibration effects occurring, normally the central plane thereof. It mayalso be satisfactory to provide a respective damping layer withassociated counter-elements on the inside of the outer member as well asalso on the opposite side of a part associated with the body of the toolor other article, for example a chamber in this body.

In a particular embodiment of the article a counter-element having onboth sides thereof damping layers located between it and the insides ofthe outer members, is arranged in a chamber provided between two outermembers. This is particularly favourable inter alia because the outermembers associated with the body of the tool or article have a largespacing from the neutral fibre layer, so that high stiffness and gooddamping effect results therefrom, while the space therebetween isutilized for the accommodation therein of the counter element. The outerperiphery and/or the inner periphery of the counter-element may besupported on the body of the article in a centering manner.

In accordance with a fundamental idea of the invention, a furtherparticular embodiment consists in that at least one damping layer formsa part of the force path between two parts of the body of the articlewhich are in mutual torque-transmitting connection. Owing to suchinclusion of the damping layer in the force path during the operation ofthe article a further direction (in the peripheral sense) in the stressstate of the damping layer becomes effective, this having a favourableeffect upon the damping. The counter-element which is located on theside of the damping layer which is remote from that part of the body ofthe article which is connected together with the work region thereofmay, in such an article, be formed directly by another portion of thebody of the article.

As in the other embodiments referred to, in such an embodiment thecounter-element is a part which is not rigidly or non-rotatablyconnected to a work region of the article, for example the peripheralregion supporting the teeth of a circular saw blade, but rather is apart which is permitted a certain mobility relatively to the part of thebody of the article which is rigidly connected to the work region, sothat the damping mechanism discussed is realized in the desired mannerwith a shear stress loading of the damping layer.

The construction of the multiple-part body of the article and thearrangement of one or more damping layers may be effected in variousways, so that different points of view and requirements may be takeninto account.

In an advantageous embodiment two parts of the body of the article whichare in connection by one or more damping layers located in the forcepath are supported on each other in a centering manner. This ensures,for the attainable damping behaviour, perfect positioning of the twoparts relative to each other.

Two outer members provided in a symmetrical arrangement of the articlemay be provided on a part of the body of the article which is designedfor the initiation of the torque, whereas a middle portion of a secondpart of the body of the article supporting the work region is arrangedto lie therebetween by its damping layers deposited on its two sides; orthe outer members are provided on a part of the body of the articlewhich forms or comprises the work region, wherein then a portion of theother part of the body of the article extends therebetween by itsassociated damping layers.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described further, by way of example, withreference to the accompanying drawings, in which:

FIGS. 1 to 6 show various embodiments of circular saw tools in axialsection, the portion of the tool below the axis being omitted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In each of the embodiments according to FIGS. 1 to 3, a main part 4 of atool body 5 is provided with a central bore 1; in its peripheral region2 it supports teeth 3, and it comprises two circular annular chambers 6which are delimited by outer members 7. The members 7 are regarded inthis case as parts of the tool body 5, and each is securely connected bycircularly extending weld seams 8, 9 to the main part 4 and therefore tothe peripheral region 2 which supports the teeth 3. They thus formsupporting elements of the tool body and also absorb the mechanicalloads occurring during the operation of the tool, inclusive of thefriction forces acting from outside. Moreover they can conduct away heatproduced, in particular from the teeth 3. The connection of the outermembers 7 to the main part 4 of the tool may alternatively be effectedby rivetting other suitable fixing means in a manner different from theconstruction illustrated, and is performed after the elements to beaccommodated in the chambers 6 have been positioned.

In the embodiment according to FIG. 1, a damping layer 12 is providedbetween the circular plane surface 10 forming the base of each chamber 6and a circular annular counter-element 11 (e.g. of steel or anothermetal or alloy); the damping layer 12 is preferably made of a syntheticresin adhesive having visco-elastic behaviour and has a thickness whichfavourably lies in the range of from 0.01 to 0.2 mm or may even begreater. The material of the damping layer has advantageously a highelasticity and a hardness which is not too great. For high damping ashear modulus G=(0.2 to 2)·10⁹ dyn/cm² at frequencies of from 1 to 5 kHzis recommended.

The counter-elements 11, the thickness of which preferably amounts to afew tenths of a millimeter, or more, are spaced at the inner and outeredge 11a, 11b as well as at the outer surface 11c from the surfaces ofthe parts 4 and 7 of the tool body facing them, so that they areindependent of the tool body or a part supporting the teeth,respectively. Upon the occurrence of vibrations, each of thecounter-elements 11 tends to move relatively to the main part 4 of thetool body, whereby shear stresses are produced in the damping layers 12,which in consequence provide a high damping effect.

With all this, the damping layers 12 with the counter-elements 11 arelocated completely protected within the regions limited by the outermembers 7. The thickness of the outer members 7 may in particular amountto from 0.2 mm to 0.8 mm or, however, may even be still greater.

In the embodiment according to FIG. 2, the outer members 7 of the toolbody are associated with damping layers 22 and counter-elements 21 whichare of the kind described above in conjunction with FIG. 1, thestatements made in respect of the damping mechanism applyingcorrespondingly. In the present case the damping layers 22 have arelatively large spacing from the central plane M of the tool, thisbeing particularly favourable in respect of the damping effect.

Furthermore, as illustrated in FIG. 3, damping layers 12, 22 andcounter-elements 11, 21 may be provided on the outer members 7 as wellas on the surfaces 10 of the main part 4 of the tool body.

The particular embodiments of the circular saw tool illustrated in FIGS.4 and 5 are constructions in which the tool body consists of two parts14 and 15 (FIG. 4) or 24 and 25 (FIG. 5), respectively, which areconstructed in the form of rings or annular discs and which support eachother in the radial direction in a centering manner. One (the radiallyouter) part 15 or 25, respectively, comprises the peripheral regionwhich supports the teeth 3, whereas the other (radially inner) part 14or 24, respectively, contains the central bore 1 and is designed toinitiate the driving torque.

In the embodiment according to FIG. 4, the part 14 comprises a disc body16 which extends symmetrically in relation to the central plane M andthe outer periphery of which is chamfered in a roof-like manner; itsedge region 19 is formed by the apex of the chamfer and may be aflattened edge, and its abuts a cylindrical inner surface 20 of theother part 15 in such a manner that the two parts fit into each otherwithout clearance and have the same concentric position in relation tothe axis of rotation D of the tool. The peripheral region 2 forming theteeth-supporting part of the tool body is securely connected bycircularly extending weld seams 18 to two outer members 17 whose inneredges 17a are spaced from the corresponding cylinder surface on ahub-like body 14a of the other part 14. Damping layers 32, consistingpreferably of an adhesive having visco-elastic properties, in particulara synthetic resin adhesive, are provided between the outer members 17and the disc-body 16 and form the torque-transmitting members betweenthe parts 14, 16 and 15, 17 of the tool body.

Whereas in the embodiments according to FIGS. 1 and 3 thecounter-element 11, 21 located on the damping layers 12, 22 are eachparts which are completely separate from the tool body proper 5, in theconstruction according to FIG. 4 and likewise in that according to FIG.5 the counter-element located on the damping layer is formed by a partwhich must be regarded to belong to the tool body, but which, in thepresent case also, is not rigidly or non-rotatably connected to theperipheral region supporting the teeth, but which is merely radiallysupported relatively to the latter. The construction and the arrangementis made in such a manner that, upon the occurrence of vibrations,relative movements are possible between the parts adjacent the dampinglayer 32 and thus the damping layer is subjected to shear stresses,additionally the peculiarity existing in this case that a further axisor direction of the shear stress state leads to an additional dampingeffect.

In the embodiment according to FIG. 5, a central disc-body 26 extendsradially inwardly from the part 25 of the tool body which comprises theperipheral region 2 supporting the teeth 3, whereas the other part 24into which the driving motion is introduced comprises two outer members27 which are securely connected to it or to a hub body 24a associatedtherewith, respectively, by means of circular annular weld seams 28. Inthe present case also, damping layers 32 constitutingtorque-transmitting and vibration damping members are provided betweenthe outer members 27 and the disc-body 26. The outer edges 27a of theouter members 27 have a small spacing from the opposed cylindricalsurfaces of the peripheral region 2 supporting the teeth 3. As in theconstruction according to FIG. 4, a centering support other of the twoparts 24 and 25 of the tool body relative to each is provided by thefact that an edge region 29 of the disc-body 26, which is chamfered onboth sides at its periphery, abuts a cylindrical outer surface of theother part 24, 24a.

FIG. 6 illustrates an embodiment of a circular saw tool whose tool body45 consists of a part 43 which comprises the peripheral region (workregion) 2 with the teeth 3, a hub part 44 and two outer members 47 whichare connected to the two other parts 43 and 44 by weld seams 48 or inanother suitable manner. The parts referred to form a circular annularchamber 46 in the interior of the tool body 45 in which acounter-element 49 is disposed. Visco-elastic damping layers 42 arelocated on both sides thereof, and by means of them it is in connectionwith the outer members 47. In a radial direction the counter-element 49is supported on cylindrical surfaces 50, 51 of the parts 43 and 44 bythe apices of chamfered regions 49a and 49b located at the outerperiphery and at the inner periphery. In this construction thecounter-element 49 is accommodated in a particularly favourable mannerin a central region of the tool. In this region, supporting parts of thetool body would not contribute to the stiffness as much as the outermembers arranged at a spacing from the central plane M (neutral fibrelayer).

In the various embodiments explained the outer members consistpreferably of the same material as the other parts of the tool body, inparticular of steel. However, the use of other work materials is notexcluded.

The term teeth is to be understood to comprise all constructions whichare usual for circular saws, including cutting blades of tool steel,hard metal, or ceramic, either in a secure connection or in a clampedconnection.

As has been explained above in connection with circular saws, otherrotatably drivable tools may also be constructed in a correspondingmanner in accordance with the invention, such as circular cutters.

In the embodiments of circular saw tools discussed, the work region ofthe tool body is formed by the peripheral region supporting the teeth.However, the invention comprises also tool constructions in which thework region of the tool body may extend at least partially at the frontface, appropriate cutting blades or the like then being present there.This applies for example to end milling cutters.

Moreover the invention extends also to other articles of the kindreferred to further above or initially, in which vibration and noiseproblems exist, thus inter alia in particular also rotating driveelements, such as gear wheels, rotating parts of belt drives etc., aswell as similar machine elements. Statements made in the explanation ofthe embodiments of circular saw tools in respect of the tool body andother parts applies in the appropriate sense and correspondingly to thebody and to further associated parts of such drive or machine elements.

We claim:
 1. A vibration-damped, disc-like rotatable tool having tworadial faces, a central axis of rotation, a rotary drive means fordriving the tool about said axis of rotation, a central plane extendingradially from the axis, and a work region in the peripheral region ofthe tool adapted to interact with another article comprising:a firstmember comprised of two like annular disc members extendingsubstantially parallel to said central plane of the tool spacedequidistantly therefrom to form an annulus therebetween and securelyconnected at their outer peripheries to the work region, the innerperipheries of said disc members being spaced from the rotary drivemeans; a second disc-like annular member extending radially within saidannulus in spaced relation to the adjacent walls of said discs of saidfirst outer member and having a central radial plane coincident withsaid central plane of the tool and connected at its inner periphery tosaid rotary drive means to be driven about the axis of rotation thereby;and a damping layer of visco-elastic material in said annulus on eachside of said second disc-like member solely connecting said first andsecond annular disc members together so that said damping layers solelytransmit therethrough the torque from said rotary drive means and saidsecond member to said first member and shear stresses occur in saiddamping layers.
 2. A rotatable tool as claimed in claim 1 wherein saidfirst annular member is centrally supported with respect to said centralplane by said damping layers on said second annular member.
 3. Arotatable tool as claimed in claim 1 wherein said first annular memberis integral with the peripheral region of the tool.
 4. Avibration-damped, disc-like rotatable tool having two radial faces, acentral axis of rotation, a rotary drive means for driving the toolabout said axis of rotation, a central plane extending radially from theaxis of rotation, and a work region in the peripheral region of the tooladapted to interact with another article comprising:a first disc-likeannular member having a central radial plane coincident with the centralplane of the tool extending radially and connected at its outerperiphery to said work region; a second member comprised of two likeannular disc members extending substantially parallel to said firstmember on opposite sides of said first member equidistantly spacedtherefrom and connected at their inner peripheries to said rotary drivemeans and being in spaced relation at their outer peripheries to saidwork region; and a damping layer of visco-elastic material in each spaceon opposite sides of said first member solely connecting said first andsecond disc members together so that said damping layers solely transmittherethrough the torque from said rotary drive means and said seconddisc member to said first member and shear stresses occur in saiddamping layers.